Is it possible to render an object just with the normal map?
A normal map will allow to simulate high poly details on a low poly mesh (using light) but won't change the shape of it. You won't be able to remove the visibility of the topology on borders with good result. You can try a fresnel or layer weight node to mix a transparent but this will make holes. This could work on a volume but not on a surface shader.  

All you can really do is adding a subsurf to add some topo and smooth the borders.